One of my first posts on GuitarGear.org was entitled, “Turn that F&%kin’ Thing Down!!!.” In that post, I introduced the Dr Z. Air Brake attenuator. Yes, I’m still using it, but I continued to search for that volume sweet spot. Even with an attenuator, my volume’s still pretty loud, but it’s much more controllable now than when I didn’t have the attenuator. However, an attenuator can only take you so far, because it is essentially a power resistor. It doesn’t reduce your power in any way. But all that’s changed…
Introducing the THD Yellow Jacket
I discovered this in the latest issue of Premier Guitar in the DIY amp column (don’t remember the original column title, sorry). Essentially, the Yellow Jacket is a combination adapter/tube replacement for 6V6, 6L6, EL34, and 7591 tube amps. Using lower-output EL34’s the output wattage of your amp is significantly reduced, thus lowering your amp’s volume. The following comes right off the THD web site:
What are Yellow Jackets®?
Yellow Jackets® Converters are a type of specialized adapters which permit the use of EL84/6BQ5 power tubes in place of 6V6, 6L6, EL34, and 7591 types.
How do they work?
They give you simple Class-A operation from any amp.Yellow Jacket® Converters not only rearrange the pin locations of the tubes, but also provide the necessary current limiting on the screens and cathode as well as blocking the amplifier’s grid bias voltage, while configuring the EL84 in a Class-A, Self-adjusting cathode-bias circuit. In other words, there are no adjustments to make and no modifications necessary, you simply plug the Yellow Jackets® into the amp’s output tube sockets, (in cathode-bias amplifiers) screw the ground wires under one of the output tube socket mounting screws, plug the provided EL84’s into the Yellow Jackets®, turn on the amp and play.
How will they change my amplifier?
It’s like getting a whole new amplifier! In Champ and Deluxe type amplifiers, the Yellow Jackets® output is smooth, strong and more even than with the stock 6V6s. When the Yellow jackets® Converters are installed in larger amplifiers intended for 6L6s or EL34 output tubes, the high plate and screen voltages are reduced as well as current limited to protect the EL84 and to drop output power. When a pair of Yellow Jackets® are used in a Marshall 50 watt or similar amplifier, the overall power drops to about 20 watts and takes on more of the character of an old Vox AC30. The distortion is smoother and more even and the output is both substantially reduced and more compressed due to the Class-A nature of the Yellow Jackets®. In a 100 watt amp like a Twin Reverb or Marshall 100, either two or four Yellow Jackets® can be used. If only two are used and the other two sockets are left empy, the output is dropped to about 20 watts. With four in place, the amp puts out about 40 watts and takes on a whole new warmth and richness.
In the cases of the YJ7591 converters, the overall ouput power remains the same, but the sound becomes fuller and the extinct 7591 are replaced with common and inexpensive EL84 tubes. In old Ampeg Reverb Rockets and the like, you experience a warmth and sweetness that you could never get with the now unavailable 7591 tubes.
Will they hurt my amp?
No! Yellow Jacket® converters are safe for all amplifiers and transformers. As all Yellow Jacket® Converters internally limit voltage and current they put no extra strain on amplifiers’ power and output transformers or internal components. Using the Yellow Jackets® in higher powered amplifiers actually reduces the strain on the transformers and internal components because it reduces the overall wattage of the system. Furthermore, the heater (or filament) current of the EL84 is lower than that of the 6L6, EL34 or 7591, so the Yellow Jacket® will reduce the strain on the filament windings of the power transformer as well.
I called THD about the Yellow Jacket to find out what was appropriate for my amp. Most Yellow Jackets come in two flavors: a Standard that lowers your output by 50-70%, and a Triode version that lowers your output by 70%-90%. I went with the Triode version for my Hot Rod so I could essentially have a 5Watt amp. According to the guy at THD, the great thing about the Yellow Jacket is that you don’t lose your tone. Just reduce your power. The Triode version also has a smoother distortion and earlier breakup – at lower volumes, which is what I want for my home recording, and playing Church.
So if you’re in search of lowering your volume but not having to invest in a smaller amp, look no further! The THD Yellow Jacket is it!
Guitar Gear 